1. Field of the Invention
The invention generally relates to an illumination module and a projection apparatus, and more particularly, to an illumination module improving illumination, a projection apparatus having the same, and a light source control method.
2. Description of Related Art
Besides such projection apparatus that provides color images by sequentially producing red, green, and blue light through an ultra high pressure (UHP) lamp (for emitting a white light) and a color wheel, a projection apparatus which uses red, green, and blue light emitting diodes (LEDs) as its light source has been provided along with the development of display technologies.
A projection apparatus uses LEDs as its light source, the light beams emitted by the red, green, and blue LEDs are combined by a light combination system, so that different color light beams along different transmission directions could be conducted to the same direction. The brightness of such a projection apparatus is determined by the brightness of the LEDs. In particular, the green LED is the major brightness contributor. Accordingly, the brightness of the entire projection apparatus is most limited by the light emission efficiency of the green LED. However, since an existing green LED has low light emission efficiency, it is not capable of being used as the light source of a high-brightness projection apparatus (for example, above 2000 ANSI lumens).
Several patents related to projection apparatuses have been disclosed. For example, an illumination device including a light source and a phosphor color wheel is disclosed in U.S. Pat. No. 7,651,243, wherein the light source sequentially irradiates the phosphor color wheel containing a plurality of blocks to produce light beams in different colors.
Additionally, a green light source device producing green light by irradiating a green phosphor plate with an excitation light source is disclosed in U.S. publication No. 20090268167. Moreover, a technique of sequentially exciting phosphor powder on a light transparent substrate by using an excitation light beam so as to sequentially produce red and green light is disclosed in U.S. publication No. 20090284148.